ABSTRACT
A person can have an obligation to do X only if it is within . his capacity to do X. Accordingly, it makes sense for A to tell B that he has an obligation to do X only if A believes that it is within B’s capacity to do X. “You (B) have an obligation to contribute $1,000 to your political party” is senseless if A knows that B has no funds to give. A’s purpose (we will assume) is to guide B’s conduct, but B could not possibly act upon the guidance A offers. This convention governing the use of “obligation” to guide conduct is summarized in the generalization “‘Obligation’ implies ability.”
